Can you take bosentan while breastfeeding?
What LactMed says
The National Library of Medicine’s own summary, quoted in full. We do not write a verdict of our own on this question, and we do not compress theirs into a label.
A study in one patient taking bosentan during breastfeeding found very low levels in milk. Another woman breastfed her preterm newborn while taking bosentan and sildenafil with no adverse effects reported. Amounts ingested by the infant are far below doses given to treat infants and would not be expected to cause any adverse effects in breastfed infants.
Quoted from Bosentan — Drugs and Lactation Database (LactMed®), National Institute of Child Health and Human Development, revised August 15, 2025.
What LactMed would consider instead
LactMed ends this record by naming the drugs it would consider in place of bosentan. Whether any of them fits depends on what you are treating — this is the database’s list, not a recommendation from us.
- Epoprostenol
- Nitric Oxide
- Sildenafil
- Treprostinil
How much bosentan gets into breastmilk
Maternal Levels. A woman breastfeeding her 21-month-old infant was taking 125 mg bosentan twice daily and 20 mg sildenafil 3 times daily to treat pulmonary arterial hypertension. She pumped three milk samples collected at home over 24 hours on days 637 and 651 postpartum. Bosentan milk concentrations ranged from 23.2 mcg/L at 10 hours after the morning dose to 86.1 mcg/L at 6 hours after the morning dose. The average steady-state milk concentration of bosentan was 49 mcg/L. The patient’s infant was breastfed 3 times daily. The estimated infant doses via milk on the two days were 0.29 and 0.60 mcg/kg in this partially breastfed infant. A fully breastfed infant might receive a dosage as high as 7.43 mcg/kg daily, which translate into a relative infant dose of 0.24%. This dosage would also be far below the infant therapeutic dosage of 4 mg/kg.
Infant Levels. Relevant published information was not found as of the revision date.
What has been seen in breastfed infants
A 23-year-old woman with congenital heart disease and pulmonary hypertension was treated during pregnancy with bosentan and sildenafil in unspecified dosages. These drugs and warfarin were continued postpartum. Her infant was delivered at 30 weeks by cesarean section and weighed 1.41 kg at birth. She nursed the infant in the neonatal intensive care unit for 11 weeks “with good outcome” according to the authors, but the infant died at 26 weeks from a respiratory syncytial virus infection.
A woman breastfeeding her 21-month-old infant was taking 20 mg of sildenafil 3 times daily and 125 mg of bosentan twice daily to treat pulmonary arterial hypertension. The drugs were begun more than 6 months postpartum. The mother did not report any possible adverse effects, serious health problem or hospitalization of the infant in the period from birth until day 651 postpartum when the infant continued to be partially breastfed.
Effects on milk supply
Relevant published information was not found as of the revision date.
Frequently asked questions
Can you take bosentan while breastfeeding?
A study in one patient taking bosentan during breastfeeding found very low levels in milk. The full record is quoted on this page, and the decision is one to make with the person who prescribed it — LactMed itself states it is not a substitute for professional judgement.
What can I take instead of bosentan while breastfeeding?
LactMed lists Epoprostenol, Nitric Oxide, Sildenafil, Treprostinil as alternate drugs to consider. That is the database's own list for this drug — whether any of them suits you depends on what you are treating.
Does bosentan pass into breastmilk?
LactMed's measured drug levels for bosentan are quoted in full on this page, under "How much gets into breastmilk".
Do I need to pump and dump after taking bosentan?
LactMed does not frame its records that way — it reports measured drug levels in milk and what has been observed in breastfed infants, which is what this page quotes. "Pump and dump" advice for a specific drug and dose should come from your clinician or a pharmacist, not from a general rule.
More on bosentan
LactMed states that the information it presents is not a substitute for professional judgement, and that you should consult your healthcare provider for breastfeeding advice related to your particular situation. Nothing on this page is medical advice.